> ## Documentation Index
> Fetch the complete documentation index at: https://docs.upsonic.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Dependencies

> Declare and validate inter-skill dependencies

## Overview

Skills can declare dependencies on other skills. The Skills system validates these at load time — detecting missing dependencies and circular references.

## Declaring Dependencies

Add a `dependencies` list in your `SKILL.md` frontmatter:

```yaml theme={null}
---
name: advanced-review
description: Advanced code review with data analysis
dependencies:
  - code-review
  - data-analysis
---

# Advanced Review

This skill builds on code-review and data-analysis skills...
```

## Validation Behavior

### Default Mode (Warnings)

By default, missing or circular dependencies produce warnings but don't block loading:

```python theme={null}
from upsonic import Agent
from upsonic.skills import Skills, LocalSkills

skills = Skills(loaders=[LocalSkills("./my-skills")])
# Logs: WARNING - Skill 'advanced-review' has missing dependencies: code-review

agent = Agent(
    model="anthropic/claude-sonnet-4-6",
    name="Agent",
    role="Reviewer",
    goal="Review code",
    skills=skills,
)

result = agent.print_do("Review this module for issues.")
```

### Strict Mode (Errors)

Enable `strict_deps=True` to raise a `SkillValidationError` on dependency issues:

```python theme={null}
from upsonic.skills import Skills, LocalSkills

try:
    skills = Skills(
        loaders=[LocalSkills("./my-skills")],
        strict_deps=True,
    )
except Exception as e:
    print(f"Dependency error: {e}")
```

## Circular Dependencies

The system uses DFS-based cycle detection. If skill A depends on B and B depends on A:

* **Default mode**: Logs a warning with the cycle path
* **Strict mode**: Raises `SkillValidationError` with cycle details

## Inline Skills with Dependencies

```python theme={null}
from upsonic import Agent
from upsonic.skills import Skills, Skill, InlineSkills

base_skill = Skill(
    name="formatting",
    description="Output formatting standards",
    instructions="Use consistent formatting...",
    source_path="",
    scripts=[],
    references=[],
)

advanced_skill = Skill(
    name="report-writing",
    description="Professional report writing",
    instructions="Write professional reports following formatting standards...",
    source_path="",
    scripts=[],
    references=[],
    dependencies=["formatting"],
)

skills = Skills(loaders=[InlineSkills([base_skill, advanced_skill])])

agent = Agent(
    model="anthropic/claude-sonnet-4-6",
    name="Report Writer",
    role="Business Writer",
    goal="Create professional reports",
    skills=skills,
)

result = agent.print_do("Write a quarterly business report for Q4 2025.")
```

## Parameters

| Parameter     | Type   | Default | Description                                            |
| ------------- | ------ | ------- | ------------------------------------------------------ |
| `strict_deps` | `bool` | `False` | Raise errors instead of warnings for dependency issues |